The RB1 has been designed to replace pigmy filament bulbs in Voltage detectors such as the Drummond range of voltage indicators. The pigmy bulb indication is by various brightness of the filament for different voltages the RB1 displays its voltage levels by different intensities and different arrays and colours of LEDs.

The RB1 has been designed to be used with a 2000Ω resistor in series with it. A special high integrity resistor is included with each RB1.